Similar to variations these are actually a lot easier to find. They have existed since about the mid 90s I think. I like them be.cause there are many versions such as blue copper platinum but one of the more common ones are the gold parallels which can be found in any regular topps product and theyre usually numbered corresponding to the year of its release (/2006,/2010). The reason I am writing about this is that this year I seem to not have any of these at all. I collect as of this year only 2 sports: baseball and football and this year after opening about 15 packs of cards I have not gotten any parallels. I have one from every year since I started collecting (2006) from one of the 2 sports sets but that seems to me like a weird thing. Since Ive started collecting I have bought all my cards at retail stores but why no parallels? they seem to come 1:4 packs or so right? not the case for me this year. I see this as lucky though since it has allowed me to get more base cards for my sets. Even if I dont get any parallels for this years products one might just turn up in a repack box that I might buy some day or in a pack that I buy soon.